It is well known that hydrogen can be purified using cryogenic purification methods; see U.S. Pat. Nos. 3,628,340, 3,839,847, 4,043,770 and 4,242,875 as illustrative art. Activated carbon is a widely used adsorbent for purifying various substances.
It is known in the art that undesirable levels of boron and/or phosphorus can render silicon unsuitable for semiconductor use. It is also known in the art that silane in hydrogen can be thermally decomposed to produce silicon. It is also known that traces of boron and phosphorus should be removed from silane prior to converting it to electronic grade silicon.
U.S. Pat. No. 3,041,141 discloses use of amines to reduce boron levels in silane.
British No. 851,962 discloses use of alkaline earth metal hydrides to reduce boron levels in silane.
It is believed that the ability of activated carbon to remove boron and phosphorus from hydrogen has not been previously described.